RFR: 8300491: SymbolLookup::libraryLookup accepts strings with terminators

[Maurizio Cimadamore]

There is a difference in behavior between `System::loadLibrary` and `SymbolLookup::libraryLookup(String)`. While the former catches library names containing NULL chars (because, internally it uses Path/File logic, which reject those), `SymbolLookup` does not. As a result, it is possible to load libraries such as `libGL.so\0foobar`, because the string is passed directly to `dlopen`.

A similar issue arises when we consider `SymbolLookup::find`, as the name is again sent unmodified to `dlopen`. In reality, some filtering *does* happen in that case, as the native code calls `GetStringUTFChars`:

https://docs.oracle.com/en/java/javase/20/docs/specs/jni/functions.html#getstringutfchars

Which encodes the NULL chars in a different form:

https://docs.oracle.com/en/java/javase/20/docs/specs/jni/types.html#modified-utf-8-strings

So, in practice, even if the input is not validated, a call to `find` with one or more NULL chars is unlikely to succeed.

In this patch I have added several checks to make sure that:
* the name of library passed to `libraryLookup(String)` does not contain `\0` and, if so, throw `IllegalArgumentException` (which is already covered by current spec;
* the name of a symbol passed to `SymbolLookup::find` does not contain `\0` and, if so, return empty optional. This required changes on all the lookups we implement.

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Commit messages:
 - Initial push

Changes: https://git.openjdk.org/jdk/pull/14126/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14126&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300491
  Stats: 33 lines in 5 files changed: 33 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14126.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14126/head:pull/14126

PR: https://git.openjdk.org/jdk/pull/14126